Lipids are indispensable ingredients in the food and cosmetics industries, and they are important precursors in the biodiesel and biochemical industries. Many oleaginous microorganisms produce lipids, including the well-characterized yeast Yarrowia lipolytica. 
The lipid yield of oleaginous organisms can be increased by the up-regulation, down-regulation, or deletion of genes implicated in a lipid pathway. Recent data suggests that the activity of the diacylglycerol acyltransferase protein DGA1 may be a significant factor for accumulating high levels of lipids in oleaginous organisms. For example, it was reported that the up-regulation of the native Y. lipolytica diacylglycerol acyltransferase protein DGA1 in Y. lipolytica significantly increases its lipid yield and productivity (METABOLIC ENGINEERING 15:1-9 (2013)).
The Y. lipolytica DGA1 protein is a type 2 diacylglyecrol acyltransferase encoded by the Y. lipolytica diacylgylcerol acyltransferase gene DGAT2. DGA1 is one of the key enzymes in the lipid pathway, involved in the final step of triacylglycerol (“TAG”) synthesis. Triacylglycerols are the major form of storage lipids in Y. lipolytica. Yeast also contain a type 1 diacylglycerol acyltransferase gene DGAT1, which encodes the DGA2 protein.
Diacylglycerol acyltransferase genes can be introduced into a host genome to affect lipid production and composition, including the DGA1 and DGA2 genes from other organisms. For example, other oleaginous yeasts, such as Rhodosporidium toruloides and Lipomyces starkeyi, are able to accumulate significantly more lipids than wild type Y. lipolytica strains, and the expression of DGA1 proteins from organisms with higher native lipid production levels has a greater effect on Y. lipolytica lipid production than the overexpression of native Y. lipolytica DGA1 (U.S. Ser. No. 61/943,664 and PCT Patent Application No. PCT/US15/017227; hereby incorporated by reference).
Additionally, genes involved in the breakdown of lipids or in pathways that draw flux away from lipid biosynthesis have been deleted to increase a cell's lipid content. For example, Dulermo et al. demonstrated (feat the deletion of the triacylglycerol lipase gene TGL3 nearly doubled the total lipid content accumulated by Y. lipolytica (BIOCHEMICA BIOPHYSICA ACTA 1831:1486-95 (2013)).
The successful upregulation of functional enzymes, however, is unpredictable at best. For example, other experiments have shown that expressing DGA1 from Mortierella alpine has no significant effect on Y. lipolytica lipid content (U.S. Pat. No. 7,198,937; hereby incorporated by reference). Similarly, expressing DGA2 has been shown to have no significant effect on the lipid content of yeast in the absence of other genetic modifications.